Answering the long-felt need for bleach-containing aqueous liquid detergent compositions, European Patent Application 293 040 and 294 904, have described aqueous detergent compositions having a pH above 8, containing an anionic surfactant at conventional levels, and a solid peroxygen bleach, suspended in a specific water/solvent medium, which medium was found to give the required chemical stability to the composition.
In such compositions however, particular attention has to be given to the physical stability of suspended particles in the liquid medium.
One option is represented by e.g. copending U.K. Application No. 8926620.9, describing liquid detergent compositions in which solid particles, in particular particles of a peroxygen compound, are suspended by means of a structured surfactant phase (surfactant "neat phase"). There is a need, however, for suspending systems which involve easier processing, compared to structured surfactant phases.
Although not for the purpose of suspending peroxygen bleach particles, structured surfactant phases have been described in various patent documents. In particular EP-A-79 646, EP-A-86 614, EP-A-203 660 and EP-A-295 021 describe liquid detergent compositions containing suspended builder particles where one or more "salting-out" electrolytes, or "surfactant desolubilizing" electrolytes are used, to build structured phases with the surfactant materials.
Such electrolytes include, among many other substances, silicates, and need to be used at substantial levels, i.e. above 5%, in order to perform their "salting-out" effect.
Other patent documents disclosing the use of silicates in cleaning/detergent compositions of the suspending type include GB-A-2031455, and GB-A-1342612 wherein the solid materials to be suspended include abrasives and water-insoluble phosphate builder salts, but do not encompass peroxygen bleach particles. Actually, GB-A-2158453 which mentions perborate as a possible bleaching ingredient in liquid compositions of the suspending type specifically advocates that the compositions must be free of silicate, and instead must contain a carboxylic antigelling agent.
Silicates have also been widely described as alkalinity-building ingredients of aqueous thixotropic liquid compositions used for e.g. automatic dishwashing purposes. Representative of this art is EP 315 024, disclosing levels of silicate in the range of 25% to 40%.
It has now surprisingly been found that low levels of silicate can efficiently suspend peroxygen-bleach particles in liquid detergent compositions of the type described in EP-A-293 040, with only a moderate increase in the viscosity of the composition.
The present suspension system does not involve any specific processing difficulty; furthermore the presence of silicate brings such advantages as increased alkalinity and increased washing-machine compatibility.
The present invention therefore provides perfectly phase-stable aqueous liquid detergent compositions containing a solid peroxygen bleach compound, a liquid phase consisting of water and a water-miscible organic solvent, and low levels of silicate to suspend the peroxygen bleach particles in the liquid phase.